Minimally invasive medical techniques are aimed at reducing the amount of extraneous tissue which is damaged during diagnostic or surgical procedures, thereby reducing patient recovery time, discomfort, and deleterious side effects. Millions of surgeries are performed each year in the United States. Many of these surgeries can potentially be performed in a minimally invasive manner. However, only a relatively small number of surgeries currently use these techniques due to limitations in minimally invasive surgical instruments and techniques and the additional surgical training required to master them.
Advances in minimally invasive surgical technology could dramatically increase the number of surgeries performed in a minimally invasive manner. The average length of a hospital stay for a standard surgery is significantly longer than the average length for the equivalent surgery performed in a minimally invasive surgical manner. Thus, the complete adoption of minimally invasive techniques could save millions of hospital days, and consequently millions of dollars annually in hospital residency costs alone. Patient recovery times, patient discomfort, surgical side effects, and time away from work are also reduced with minimally invasive surgery.
The most common form of minimally invasive surgery is endoscopy. Probably the most common form of endoscopy is laparoscopy, which is minimally invasive inspection and surgery inside the abdominal cavity. In standard laparoscopic surgery, a patient""s abdomen is insufflated with gas, and cannula sleeves are passed through small (approximately xc2xd inch) incisions to provide entry ports for laparoscopic surgical instruments.
The laparoscopic surgical instruments generally include a laparoscope for viewing the surgical field, and working tools defining end effectors. Typical surgical end effectors include clamps, graspers, scissors, staplers, or needle holders, for example. The working tools are similar to those used in conventional (open) surgery, except that the working end or end effector of each tool is separated from its handle by, e.g., an approximately 12-inch long, extension tube.
To perform surgical procedures, the surgeon passes these working tools or instruments through the cannula sleeves to a required internal surgical site and manipulates them from outside the abdomen by sliding them in and out through the cannula sleeves, rotating them in the cannula sleeves, levering (i.e., pivoting) the instruments against the abdominal wall and actuating end effectors on the distal ends of the instruments from outside the abdomen. The instruments pivot around centers defined by the incisions which extend through muscles of the abdominal wall. The surgeon monitors the procedure by means of a television monitor which displays an image of the surgical site via a laparoscopic camera. The laparoscopic camera is also introduced through the abdominal wall and into the surgical site. Similar endoscopic techniques are employed in, e.g., arthroscopy, retroperitoneoscopy, pelviscopy, nephroscopy, cystoscopy, cisternoscopy, sinoscopy, hysteroscopy, urethroscopy and the like.
There are many disadvantages relating to current minimally invasive surgical (MIS) technology. For example, existing MIS instruments deny the surgeon the flexibility of tool placement found in open surgery. Most current laparoscopic tools have rigid shafts and difficulty is experienced in approaching the surgical site through the small incision. Additionally, the length and construction of many surgical instruments reduces the surgeon""s ability to feel forces exerted by tissues and organs on the end effector of the associated tool. The lack of dexterity and sensitivity of surgical tools is a major impediment to the expansion of minimally invasive surgery.
Minimally invasive telesurgical systems for use in surgery are being developed to increase a surgeon""s dexterity as well as to allow a surgeon to operate on a patient from a remote location. Telesurgery is a general term for surgical systems where the surgeon uses some form of remote control, e.g., a servomechanism, or the like, to manipulate surgical instrument movements rather than directly holding and moving the instruments by hand. In such a telesurgery system, the surgeon is provided with an image of the surgical site at the remote location. While viewing typically a three-dimensional image of the surgical site on a suitable viewer or display, the surgeon performs the surgical procedures on the patient by manipulating master control devices, at the remote location, which control the motion of servomechanically operated instruments.
The servomechanism used for telesurgery will often accept input from two master controllers (one for each of the surgeon""s hands), and may include two robotic arms. Operative communication between each master control and an associated arm and instrument assembly is achieved through a control system. The control system includes at least one processor which relays input commands from a master controller to an associated arm and instrument assembly and from the arm and instrument assembly to the associated master controller in the case of, e.g., force feedback.
With advances in computer technology, it is now possible for processors to accept and interpret the wide range of quite rapid, precise hand motions made by a surgeon in manipulating the master controllers during surgery. Unfortunately, robotic arms often have responsive limitations which may be more restrictive than the controller. Furthermore, the robotic arm joints often have limits in their displacement capability or range of achievable position relative to each other. Yet further, the robotic arm and surgical instrument assemblies may have positional limits beyond which it is not possible to move.
It would be advantageous that master control movements and responsive end effector movements as displayed be as natural and comfortable to the surgeon as possible. To achieve this, certain obstacles should be overcome. One such obstacle is constraining master control movement input within bounds dictated by mechanically achievable positional movements and velocity of its associated arm and surgical instrument assembly.
It is an object of this invention to provide a method and control system whereby master control movement can be constrained to remain within limitations imposed by its associated robotic arm and instrument assembly, in an intuitive manner.
It is to be appreciated that although the method and control system of the invention is described with reference to a minimally invasive surgical apparatus in this specification, the application of the invention is not to be limited to this application only, but can be used in any type of apparatus where an input is entered at one location and a corresponding movement is required at a remote location and in which it is required, or merely beneficial, to constrain master control input to remain within limitations or constraints dictated by the corresponding movement at the remote location. Thus, the invention may find application in the fields of satellite dish tracking, handling hazardous substances, to name but two of many possible qualifying fields.
According to one aspect of the invention, there is provided a surgical method including generating a desired surgical instrument movement command signal; comparing the desired surgical instrument movement command signal with at least one preset surgical instrument movement limitation; restricting the desired surgical instrument movement command signal to yield a restricted surgical instrument movement command signal should the desired surgical instrument movement command signal transgress the preset surgical instrument movement limitation; and causing a surgical instrument to move in response to the restricted surgical instrument movement command signal.
According to another aspect of the invention, there is provided a control system including processing means arranged to generate a desired surgical instrument movement command signal; and processing means arranged to compare the desired surgical instrument movement command signal with at least one preset surgical instrument movement limitation, and to restrict the desired surgical instrument movement command signal to yield a restricted surgical instrument movement command signal should the desired surgical instrument command signal transgress the preset surgical instrument movement limitation.
In accordance with another aspect of the invention, there is provided a method of effecting control between a master and a slave of a minimally invasive surgical apparatus, the method including generating slave movement commands in response to and corresponding with master movement; inputting the slave movement commands into a simulated domain, the simulated domain having at least one preset movement limitation; determining whether or not the slave movement command transgresses the movement limitation in the simulated domain; restricting the slave movement command in the simulated domain, if it transgresses the limitation, by a value calculated to yield a restricted slave movement command not transgressing the movement limitation; forwarding the restricted slave movement command to the slave to cause the slave to move in sympathy with the restricted slave movement command; and causing a master movement command, corresponding to the value by which the slave movement command was restricted, to be sent to the master to cause the master to resist movement promoting corresponding slave movement commands which transgress the slave movement limitation set in the simulated domain.
In accordance with yet a further aspect of the invention, there is provided a control system for effecting control between a master and a slave of a minimally invasive surgical apparatus, the control system including generating means for generating slave movement commands in response to and corresponding with master movement; a simulated domain into which the slave movement commands are input prior to the slave movement commands being forwarded to the slave; at least one movement limitation set in the simulated domain; restriction means in the simulated domain for restricting the slave movement commands, should they transgress the limitation, by a calculated value so as to yield a restricted slave movement command which does not transgress the limitation; communication means for communicating the restricted slave movement command to the slave to cause the slave to move in sympathy with the restricted slave movement command; and feedback means whereby a master movement command signal, corresponding to the calculated value by which the slave movement command was restricted, is sent to the master to cause the master to resist movement promoting corresponding slave movement commands which transgress the slave movement limitation set in the simulated domain
According to another aspect of the invention, there is provided a method of transforming a velocity signal relative to a reference coordinate system into joint space by means of a transformation relationship, the method including modifying the transformation relationship to account for at least one singularity.